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WorkerThreadPool: Support daemon-like tasks (via yield semantics)

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This commit is contained in:
Pedro J. Estébanez 2024-04-09 17:26:45 +02:00
parent 71facbaa88
commit 1b104ffcd8
4 changed files with 217 additions and 77 deletions
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164
core/object/worker_thread_pool.cpp
View File

@ -35,6 +35,8 @@
#include "core/os/thread_safe.h"
#include "core/templates/command_queue_mt.h"
WorkerThreadPool::Task *const WorkerThreadPool::ThreadData::YIELDING = (Task *)1;
void WorkerThreadPool::Task::free_template_userdata() {
ERR_FAIL_NULL(template_userdata);
ERR_FAIL_NULL(native_func_userdata);
@ -391,70 +393,11 @@ Error WorkerThreadPool::wait_for_task_completion(TaskID p_task_id) {
task_mutex.unlock();
if (caller_pool_thread) {
while (true) {
Task *task_to_process = nullptr;
{
MutexLock lock(task_mutex);
bool was_signaled = caller_pool_thread->signaled;
caller_pool_thread->signaled = false;
if (task->completed) {
// This thread was awaken also for some reason, but it's about to exit.
// Let's find out what may be pending and forward the requests.
if (!exit_threads && was_signaled) {
uint32_t to_process = task_queue.first() ? 1 : 0;
uint32_t to_promote = caller_pool_thread->current_task->low_priority && low_priority_task_queue.first() ? 1 : 0;
if (to_process || to_promote) {
// This thread must be left alone since it won't loop again.
caller_pool_thread->signaled = true;
_notify_threads(caller_pool_thread, to_process, to_promote);
}
}
task->waiting_pool--;
if (task->waiting_pool == 0 && task->waiting_user == 0) {
tasks.erase(p_task_id);
task_allocator.free(task);
}
break;
}
if (!exit_threads) {
// This is a thread from the pool. It shouldn't just idle.
// Let's try to process other tasks while we wait.
if (caller_pool_thread->current_task->low_priority && low_priority_task_queue.first()) {
if (_try_promote_low_priority_task()) {
_notify_threads(caller_pool_thread, 1, 0);
}
}
if (singleton->task_queue.first()) {
task_to_process = task_queue.first()->self();
task_queue.remove(task_queue.first());
}
if (!task_to_process) {
caller_pool_thread->awaited_task = task;
if (flushing_cmd_queue) {
flushing_cmd_queue->unlock();
}
caller_pool_thread->cond_var.wait(lock);
if (flushing_cmd_queue) {
flushing_cmd_queue->lock();
}
DEV_ASSERT(exit_threads || caller_pool_thread->signaled || task->completed);
caller_pool_thread->awaited_task = nullptr;
}
}
}
if (task_to_process) {
_process_task(task_to_process);
}
_wait_collaboratively(caller_pool_thread, task);
task->waiting_pool--;
if (task->waiting_pool == 0 && task->waiting_user == 0) {
tasks.erase(p_task_id);
task_allocator.free(task);
}
} else {
task->done_semaphore.wait();
@ -470,6 +413,99 @@ Error WorkerThreadPool::wait_for_task_completion(TaskID p_task_id) {
return OK;
}
void WorkerThreadPool::_wait_collaboratively(ThreadData *p_caller_pool_thread, Task *p_task) {
// Keep processing tasks until the condition to stop waiting is met.
#define IS_WAIT_OVER (unlikely(p_task == ThreadData::YIELDING) ? p_caller_pool_thread->yield_is_over : p_task->completed)
while (true) {
Task *task_to_process = nullptr;
{
MutexLock lock(task_mutex);
bool was_signaled = p_caller_pool_thread->signaled;
p_caller_pool_thread->signaled = false;
if (IS_WAIT_OVER) {
p_caller_pool_thread->yield_is_over = false;
if (!exit_threads && was_signaled) {
// This thread was awaken for some additional reason, but it's about to exit.
// Let's find out what may be pending and forward the requests.
uint32_t to_process = task_queue.first() ? 1 : 0;
uint32_t to_promote = p_caller_pool_thread->current_task->low_priority && low_priority_task_queue.first() ? 1 : 0;
if (to_process || to_promote) {
// This thread must be left alone since it won't loop again.
p_caller_pool_thread->signaled = true;
_notify_threads(p_caller_pool_thread, to_process, to_promote);
}
}
break;
}
if (!exit_threads) {
if (p_caller_pool_thread->current_task->low_priority && low_priority_task_queue.first()) {
if (_try_promote_low_priority_task()) {
_notify_threads(p_caller_pool_thread, 1, 0);
}
}
if (singleton->task_queue.first()) {
task_to_process = task_queue.first()->self();
task_queue.remove(task_queue.first());
}
if (!task_to_process) {
p_caller_pool_thread->awaited_task = p_task;
if (flushing_cmd_queue) {
flushing_cmd_queue->unlock();
}
p_caller_pool_thread->cond_var.wait(lock);
if (flushing_cmd_queue) {
flushing_cmd_queue->lock();
}
DEV_ASSERT(exit_threads || p_caller_pool_thread->signaled || IS_WAIT_OVER);
p_caller_pool_thread->awaited_task = nullptr;
}
}
}
if (task_to_process) {
_process_task(task_to_process);
}
}
}
void WorkerThreadPool::yield() {
int th_index = get_thread_index();
ERR_FAIL_COND_MSG(th_index == -1, "This function can only be called from a worker thread.");
_wait_collaboratively(&threads[th_index], ThreadData::YIELDING);
}
void WorkerThreadPool::notify_yield_over(TaskID p_task_id) {
task_mutex.lock();
Task **taskp = tasks.getptr(p_task_id);
if (!taskp) {
task_mutex.unlock();
ERR_FAIL_MSG("Invalid Task ID.");
}
Task *task = *taskp;
#ifdef DEBUG_ENABLED
if (task->pool_thread_index == get_thread_index()) {
WARN_PRINT("A worker thread is attempting to notify itself. That makes no sense.");
}
#endif
ThreadData &td = threads[task->pool_thread_index];
td.yield_is_over = true;
td.signaled = true;
td.cond_var.notify_one();
task_mutex.unlock();
}
WorkerThreadPool::GroupID WorkerThreadPool::_add_group_task(const Callable &p_callable, void (*p_func)(void *, uint32_t), void *p_userdata, BaseTemplateUserdata *p_template_userdata, int p_elements, int p_tasks, bool p_high_priority, const String &p_description) {
ERR_FAIL_COND_V(p_elements < 0, INVALID_TASK_ID);
if (p_tasks < 0) {

19
core/object/worker_thread_pool.h
View File

@ -107,13 +107,21 @@ private:
BinaryMutex task_mutex;
struct ThreadData {
static Task *const YIELDING; // Too bad constexpr doesn't work here.
uint32_t index = 0;
Thread thread;
bool ready_for_scripting = false;
bool signaled = false;
bool ready_for_scripting : 1;
bool signaled : 1;
bool yield_is_over : 1;
Task *current_task = nullptr;
Task *awaited_task = nullptr; // Null if not awaiting the condition variable. Special value for idle-waiting.
Task *awaited_task = nullptr; // Null if not awaiting the condition variable, or special value (YIELDING).
ConditionVariable cond_var;
ThreadData() :
ready_for_scripting(false),
signaled(false),
yield_is_over(false) {}
};
TightLocalVector<ThreadData> threads;
@ -177,6 +185,8 @@ private:
}
};
void _wait_collaboratively(ThreadData *p_caller_pool_thread, Task *p_task);
protected:
static void _bind_methods();
@ -196,6 +206,9 @@ public:
bool is_task_completed(TaskID p_task_id) const;
Error wait_for_task_completion(TaskID p_task_id);
void yield();
void notify_yield_over(TaskID p_task_id);
template <typename C, typename M, typename U>
GroupID add_template_group_task(C *p_instance, M p_method, U p_userdata, int p_elements, int p_tasks = -1, bool p_high_priority = false, const String &p_description = String()) {
typedef GroupUserData<C, M, U> GroupUD;

44
tests/core/templates/test_command_queue.h
View File

@ -33,6 +33,7 @@
#include "core/config/project_settings.h"
#include "core/math/random_number_generator.h"
#include "core/object/worker_thread_pool.h"
#include "core/os/os.h"
#include "core/os/thread.h"
#include "core/templates/command_queue_mt.h"
@ -100,7 +101,7 @@ public:
ThreadWork reader_threadwork;
ThreadWork writer_threadwork;
CommandQueueMT command_queue = CommandQueueMT(true);
CommandQueueMT command_queue;
enum TestMsgType {
TEST_MSG_FUNC1_TRANSFORM,
@ -119,6 +120,7 @@ public:
bool exit_threads = false;
Thread reader_thread;
WorkerThreadPool::TaskID reader_task_id = WorkerThreadPool::INVALID_TASK_ID;
Thread writer_thread;
int func1_count = 0;
@ -148,11 +150,16 @@ public:
void reader_thread_loop() {
reader_threadwork.thread_wait_for_work();
while (!exit_threads) {
if (message_count_to_read < 0) {
if (reader_task_id == WorkerThreadPool::INVALID_TASK_ID) {
command_queue.flush_all();
}
for (int i = 0; i < message_count_to_read; i++) {
command_queue.wait_and_flush();
} else {
if (message_count_to_read < 0) {
command_queue.flush_all();
}
for (int i = 0; i < message_count_to_read; i++) {
WorkerThreadPool::get_singleton()->yield();
command_queue.wait_and_flush();
}
}
message_count_to_read = 0;
@ -216,8 +223,13 @@ public:
sts->writer_thread_loop();
}
void init_threads() {
reader_thread.start(&SharedThreadState::static_reader_thread_loop, this);
void init_threads(bool p_use_thread_pool_sync = false) {
if (p_use_thread_pool_sync) {
reader_task_id = WorkerThreadPool::get_singleton()->add_native_task(&SharedThreadState::static_reader_thread_loop, this, true);
command_queue.set_pump_task_id(reader_task_id);
} else {
reader_thread.start(&SharedThreadState::static_reader_thread_loop, this);
}
writer_thread.start(&SharedThreadState::static_writer_thread_loop, this);
}
void destroy_threads() {
@ -225,16 +237,20 @@ public:
reader_threadwork.main_start_work();
writer_threadwork.main_start_work();
reader_thread.wait_to_finish();
if (reader_task_id != WorkerThreadPool::INVALID_TASK_ID) {
WorkerThreadPool::get_singleton()->wait_for_task_completion(reader_task_id);
} else {
reader_thread.wait_to_finish();
}
writer_thread.wait_to_finish();
}
};
TEST_CASE("[CommandQueue] Test Queue Basics") {
static void test_command_queue_basic(bool p_use_thread_pool_sync) {
const char *COMMAND_QUEUE_SETTING = "memory/limits/command_queue/multithreading_queue_size_kb";
ProjectSettings::get_singleton()->set_setting(COMMAND_QUEUE_SETTING, 1);
SharedThreadState sts;
sts.init_threads();
sts.init_threads(p_use_thread_pool_sync);
sts.add_msg_to_write(SharedThreadState::TEST_MSG_FUNC1_TRANSFORM);
sts.writer_threadwork.main_start_work();
@ -272,6 +288,14 @@ TEST_CASE("[CommandQueue] Test Queue Basics") {
ProjectSettings::get_singleton()->property_get_revert(COMMAND_QUEUE_SETTING));
}
TEST_CASE("[CommandQueue] Test Queue Basics") {
test_command_queue_basic(false);
}
TEST_CASE("[CommandQueue] Test Queue Basics with WorkerThreadPool sync.") {
test_command_queue_basic(true);
}
TEST_CASE("[CommandQueue] Test Queue Wrapping to same spot.") {
const char *COMMAND_QUEUE_SETTING = "memory/limits/command_queue/multithreading_queue_size_kb";
ProjectSettings::get_singleton()->set_setting(COMMAND_QUEUE_SETTING, 1);

67
tests/core/threads/test_worker_thread_pool.h
View File

@ -38,6 +38,7 @@
namespace TestWorkerThreadPool {
static LocalVector<SafeNumeric<int>> counter;
static SafeFlag exit;
static void static_test(void *p_arg) {
counter[(uint64_t)p_arg].increment();
@ -106,6 +107,72 @@ TEST_CASE("[WorkerThreadPool] Process elements using group tasks") {
}
}
static void static_test_daemon(void *p_arg) {
while (!exit.is_set()) {
counter[0].add(1);
WorkerThreadPool::get_singleton()->yield();
}
}
static void static_busy_task(void *p_arg) {
while (!exit.is_set()) {
OS::get_singleton()->delay_usec(1);
}
}
static void static_legit_task(void *p_arg) {
*((bool *)p_arg) = counter[0].get() > 0;
counter[1].add(1);
}
TEST_CASE("[WorkerThreadPool] Run a yielding daemon as the only hope for other tasks to run") {
exit.clear();
counter.clear();
counter.resize(2);
WorkerThreadPool::TaskID daemon_task_id = WorkerThreadPool::get_singleton()->add_native_task(static_test_daemon, nullptr, true);
int num_threads = WorkerThreadPool::get_singleton()->get_thread_count();
// Keep all the other threads busy.
LocalVector<WorkerThreadPool::TaskID> task_ids;
for (int i = 0; i < num_threads - 1; i++) {
task_ids.push_back(WorkerThreadPool::get_singleton()->add_native_task(static_busy_task, nullptr, true));
}
LocalVector<WorkerThreadPool::TaskID> legit_task_ids;
LocalVector<bool> legit_task_needed_yield;
int legit_tasks_count = num_threads * 4;
legit_task_needed_yield.resize(legit_tasks_count);
for (int i = 0; i < legit_tasks_count; i++) {
legit_task_needed_yield[i] = false;
task_ids.push_back(WorkerThreadPool::get_singleton()->add_native_task(static_legit_task, &legit_task_needed_yield[i], i >= legit_tasks_count / 2));
}
while (counter[1].get() != legit_tasks_count) {
OS::get_singleton()->delay_usec(1);
}
exit.set();
for (uint32_t i = 0; i < task_ids.size(); i++) {
WorkerThreadPool::get_singleton()->wait_for_task_completion(task_ids[i]);
}
WorkerThreadPool::get_singleton()->notify_yield_over(daemon_task_id);
WorkerThreadPool::get_singleton()->wait_for_task_completion(daemon_task_id);
CHECK_MESSAGE(counter[0].get() > 0, "Daemon task should have looped at least once.");
CHECK_MESSAGE(counter[1].get() == legit_tasks_count, "All legit tasks should have been able to run.");
bool all_needed_yield = true;
for (int i = 0; i < legit_tasks_count; i++) {
if (!legit_task_needed_yield[i]) {
all_needed_yield = false;
break;
}
}
CHECK_MESSAGE(all_needed_yield, "All legit tasks should have needed the daemon yielding to run.");
}
} // namespace TestWorkerThreadPool
#endif // TEST_WORKER_THREAD_POOL_H